Vic man on trial for murdering best mate

A Melbourne man fatally stabbed his best mate in the chest after they took the drug ice and stayed up all night watching Xbox, then went to a pharmacy and told them what he'd done, a jury has heard.

Hugh William Brown has pleaded not guilty to murdering his housemate and long-term friend, Steven Warlond, 43, at the Port Melbourne apartment they shared on June 17 last year.

The opening of Brown's Supreme Court trial on Wednesday heard the pair injected ice and stayed awake watching Xbox before a dispute the next day, during which Brown stabbed his victim with a butcher's knife.

Brown, then 44, later told police Mr Warlond wanted to kill him because he thought he was a pedophile, the jury heard.

After the stabbing, Brown went to a pharmacy and told the store assistant: "Excuse me, I'm on ice and I just killed my mate. I swear on my daughter I did."

Paramedics were called but were unable to revive Mr Warlond, Crown prosecutor Andrew Grant said.

He said that earlier that month, Brown mentioned that he was depressed and being followed, but didn't know by whom.